Krebsbach Samuel, He Jianzhou, Adhikari Sushil, Olshansky Yaniv, Feyzbar Farshad, Davis Leonard C, Oh Tae-Sik, Wang Dengjun
School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL 36849, USA.
Biosystems Engineering Department, Auburn University, Auburn, AL 36849, USA.
Chemosphere. 2023 Jul;330:138661. doi: 10.1016/j.chemosphere.2023.138661. Epub 2023 Apr 10.
Biochar has recently emerged as a cost-effective solution to combat per- and polyfluoroalkyl substances (PFAS) pollution in water, but mechanistic understanding of which physicochemical properties of biochars dictate PFAS sorptive removal from water remains elusive. Herein, 15 biochars were pyrolyzed from five feedstocks (corn, Douglas fir, eucalyptus, poplar, and switchgrass) at three pyrolysis temperatures (500, 700, and 900 °C) to investigate their removal efficiencies and mechanisms of perfluorooctane sulfonate (PFOS) from water. A commercial biochar was also included for comparison. Biochar physiochemical properties, including elemental composition, pH, specific surface area (SSA), pore structure, hydrophobicity, surface charge, surface functional groups, and crystalline structure were systematically characterized. Batch sorption data showed that the Douglas fir 900 biochar (Douglas fir and 900 are the feedstock type and pyrolysis temperature, respectively; this naming rule applies to other biochars), poplar 900 biochar, and commercial biochar can remove over 95% of PFOS from water. Structural equation model (SEM) was used to elucidate which biochar properties affect PFOS sorption. Interestingly, biochar pore diameter was identified as the most critical factor controlling PFOS removal, but pore diameter/pore volume ratio, SSA, pyrolysis temperature, hydrophobicity, and elemental composition all played variable roles. Hypothetically, biochars with small pore diameters and large pore volumes had a narrow yet deep pore structure that traps PFOS molecules inside once already sorbed, resulting in an enhanced PFOS sorption. Biochars with small pore diameter, low nitrogen content, and high pyrolysis temperature were also favorable for enhanced PFOS sorption. Our findings advance the knowledge of using biochars with optimized properties to remove PFOS and possibly other similar PFAS compounds from water.
生物炭最近已成为一种经济高效的解决方案，用于应对水中的全氟和多氟烷基物质（PFAS）污染，但对于生物炭的哪些物理化学性质决定了其从水中吸附去除PFAS，目前仍缺乏深入的机理理解。在此，以五种原料（玉米、花旗松、桉树、杨树和柳枝稷）在三个热解温度（500、700和900°C）下热解制备了15种生物炭，以研究它们对水中全氟辛烷磺酸（PFOS）的去除效率和机制。还纳入了一种商业生物炭用于比较。系统地表征了生物炭的物理化学性质，包括元素组成、pH值、比表面积（SSA）、孔隙结构、疏水性、表面电荷、表面官能团和晶体结构。批次吸附数据表明，花旗松900生物炭（花旗松和900分别为原料类型和热解温度；此命名规则适用于其他生物炭）、杨树900生物炭和商业生物炭能够从水中去除超过95%的PFOS。采用结构方程模型（SEM）来阐明哪些生物炭性质会影响PFOS的吸附。有趣的是，生物炭的孔径被确定为控制PFOS去除的最关键因素，但孔径/孔体积比、SSA、热解温度、疏水性和元素组成都发挥了不同的作用。据推测，具有小孔径和大孔体积的生物炭具有狭窄而深邃的孔隙结构，一旦PFOS分子被吸附，就会将其困在内部，从而增强PFOS的吸附。小孔径、低氮含量和高热解温度的生物炭也有利于增强PFOS的吸附。我们的研究结果推进了关于使用具有优化性质的生物炭从水中去除PFOS以及可能的其他类似PFAS化合物的知识。
